Metal-oxide-semiconductor field-effect transistors (MOSFETs) are key components in microelectronic devices. With technological improvements, reductions of the source-drain channel lengths have significantly enhanced the power consumptions as well as the switching speeds. However, short channel effects such as hot-carrier transports may cause low on/off ratios and non-saturated output currents of the transistor. In addition, high resolution-patterning processes are required to define such short channel lengths, which may significantly increase the fabrication cost.